Overview

Type 2 diabetes, once known as adult-onset or noninsulin-dependent diabetes, is a chronic condition that affects the way your body metabolizes sugar (glucose), your body's important source of fuel.

With type 2 diabetes, your body either resists the effects of insulin — a hormone that regulates the movement of sugar into your cells — or doesn't produce enough insulin to maintain a normal glucose level.

More common in adults, type 2 diabetes increasingly affects children as childhood obesity increases. There's no cure for type 2 diabetes, but you may be able to manage the condition by eating well, exercising and maintaining a healthy weight. If diet and exercise aren't enough to manage your blood sugar well, you also may need diabetes medications or insulin therapy.

Symptoms

Signs and symptoms of type 2 diabetes often develop slowly. In fact, you can have type 2 diabetes for years and not know it. Look for:

Increased thirst and frequent urination. Excess sugar building up in your bloodstream causes fluid to be pulled from the tissues. This may leave you thirsty. As a result, you may drink — and urinate — more than usual.

Increased hunger. Without enough insulin to move sugar into your cells, your muscles and organs become depleted of energy. This triggers intense hunger.

Weight loss. Despite eating more than usual to relieve hunger, you may lose weight. Without the ability to metabolize glucose, the body uses alternative fuels stored in muscle and fat. Calories are lost as excess glucose is released in the urine.

Fatigue. If your cells are deprived of sugar, you may become tired and irritable.

Blurred vision. If your blood sugar is too high, fluid may be pulled from the lenses of your eyes. This may affect your ability to focus.

Areas of darkened skin. Some people with type 2 diabetes have patches of dark, velvety skin in the folds and creases of their bodies — usually in the armpits and neck. This condition, called acanthosis nigricans, may be a sign of insulin resistance.

When to see a doctor

Causes

Type 2 diabetes develops when the body becomes resistant to insulin or when the pancreas stops producing enough insulin. Exactly why this happens is unknown, although genetics and environmental factors, such as excess weight and inactivity, seem to be contributing factors.

How insulin works

Insulin is a hormone that comes from the gland situated behind and below the stomach (pancreas).

The pancreas secretes insulin into the bloodstream.

The insulin circulates, enabling sugar to enter your cells.

Insulin lowers the amount of sugar in your bloodstream.

As your blood sugar level drops, so does the secretion of insulin from your pancreas.

The role of glucose

Glucose — a sugar — is a main source of energy for the cells that make up muscles and other tissues.

Glucose comes from two major sources: food and your liver.

Sugar is absorbed into the bloodstream, where it enters cells with the help of insulin.

Your liver stores and makes glucose.

When your glucose levels are low, such as when you haven't eaten in a while, the liver breaks down stored glycogen into glucose to keep your glucose level within a normal range.

In type 2 diabetes, this process doesn't work well. Instead of moving into your cells, sugar builds up in your bloodstream. As blood sugar levels increase, the insulin-producing beta cells in the pancreas release more insulin, but eventually these cells become impaired and can't make enough insulin to meet the body's demands.

In the much less common type 1 diabetes, the immune system destroys the beta cells, leaving the body with little to no insulin.

Risk factors

Weight. Being overweight is a primary risk factor for type 2 diabetes. The more fatty tissue you have, the more resistant your cells become to insulin. However, you don't have to be overweight to develop type 2 diabetes.

Inactivity. The less active you are, the greater your risk of type 2 diabetes. Physical activity helps you control your weight, uses up glucose as energy and makes your cells more sensitive to insulin.

Family history. The risk of type 2 diabetes increases if your parent or sibling has type 2 diabetes.

Race. Although it's unclear why, people of certain races — including blacks, Hispanics, American Indians and Asian-Americans — are more likely to develop type 2 diabetes than whites are.

Age. The risk of type 2 diabetes increases as you get older, especially after age 45. That's probably because people tend to exercise less, lose muscle mass and gain weight as they age. But type 2 diabetes is also increasing dramatically among children, adolescents and younger adults.

Prediabetes. Prediabetes is a condition in which your blood sugar level is higher than normal, but not high enough to be classified as diabetes. Left untreated, prediabetes often progresses to type 2 diabetes.

Gestational diabetes. If you developed gestational diabetes when you were pregnant, your risk of developing type 2 diabetes increases. If you gave birth to a baby weighing more than 9 pounds (4 kilograms), you're also at risk of type 2 diabetes.

Complications

Type 2 diabetes can be easy to ignore, especially in the early stages when you're feeling fine. But diabetes affects many major organs, including your heart, blood vessels, nerves, eyes and kidneys. Controlling your blood sugar levels can help prevent these complications.

Although long-term complications of diabetes develop gradually, they can eventually be disabling or even life-threatening. Some of the potential complications of diabetes include:

Nerve damage (neuropathy). Excess sugar can injure the walls of the tiny blood vessels (capillaries) that nourish your nerves, especially in the legs. This can cause tingling, numbness, burning or pain that usually begins at the tips of the toes or fingers and gradually spreads upward. Poorly controlled blood sugar can eventually cause you to lose all sense of feeling in the affected limbs. Damage to the nerves that control digestion can cause problems with nausea, vomiting, diarrhea or constipation. For men, erectile dysfunction may be an issue.

Kidney damage (nephropathy). The kidneys contain millions of tiny blood vessel clusters that filter waste from your blood. Diabetes can damage this delicate filtering system. Severe damage can lead to kidney failure or irreversible end-stage kidney disease, which often eventually requires dialysis or a kidney transplant.

Eye damage. Diabetes can damage the blood vessels of the retina (diabetic retinopathy), potentially leading to blindness. Diabetes also increases the risk of other serious vision conditions, such as cataracts and glaucoma.

Foot damage. Nerve damage in the feet or poor blood flow to the feet increases the risk of various foot complications. Left untreated, cuts and blisters can become serious infections, which may heal poorly. Severe damage might require toe, foot or leg amputation.

Hearing impairment. Hearing problems are more common in people with diabetes.

Skin conditions. Diabetes may leave you more susceptible to skin problems, including bacterial and fungal infections.

Alzheimer's disease. Type 2 diabetes may increase the risk of Alzheimer's disease. The poorer your blood sugar control, the greater the risk appears to be. The exact connection between these two conditions still remains unclear.

Prevention

Healthy lifestyle choices can help you prevent type 2 diabetes. Even if you have diabetes in your family, diet and exercise can help you prevent the disease. If you've already received a diagnosis of diabetes, you can use healthy lifestyle choices to help prevent complications. And if you have prediabetes, lifestyle changes can slow or halt the progression from prediabetes to diabetes.

Get physical. Aim for a minimum of 30 minutes of moderate physical activity a day. Take a brisk daily walk. Ride a bike. Swim laps. If you can't fit in a long workout, spread 10-minute or longer sessions throughout the day.

Lose excess pounds. If you're overweight, losing 7 percent of your body weight can reduce the risk of diabetes. To keep your weight in a healthy range, focus on permanent changes to your eating and exercise habits. Motivate yourself by remembering the benefits of losing weight, such as a healthier heart, more energy and improved self-esteem.

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